U.S. patent number 4,770,559 [Application Number 07/106,818] was granted by the patent office on 1988-09-13 for positioning joint for folding ladders.
This patent grant is currently assigned to Myung Ho Kim. Invention is credited to Hoe G. Yoo.
United States Patent |
4,770,559 |
Yoo |
September 13, 1988 |
Positioning joint for folding ladders
Abstract
A positioning joint for a folding ladder comprising a first
joint member having a locking device, and a second joint member
having a relatively fitted guide-disc plate. The two joint members
are relatively pivotable about a common axis and are lockable in a
series of predetermined angular positions by engaging the locking
device provided on the first joint member in notches formed at the
peripheral edge of the other member, under the control of the
guide-disc plate.
Inventors: |
Yoo; Hoe G. (Seoul,
KR) |
Assignee: |
Kim; Myung Ho (New Hyde Park,
NY)
|
Family
ID: |
19261146 |
Appl.
No.: |
07/106,818 |
Filed: |
October 13, 1987 |
Foreign Application Priority Data
|
|
|
|
|
Mar 31, 1987 [KR] |
|
|
4310/87 |
|
Current U.S.
Class: |
403/93; 403/324;
182/163 |
Current CPC
Class: |
F16C
11/10 (20130101); E06C 1/32 (20130101); Y10T
403/598 (20150115); F16C 2350/00 (20130101); Y10T
403/32336 (20150115) |
Current International
Class: |
F16C
11/04 (20060101); F16C 11/10 (20060101); E06C
1/32 (20060101); E06C 1/00 (20060101); F16C
011/00 () |
Field of
Search: |
;182/163,164,24
;403/92,93,324 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kundrat; Andrew V.
Attorney, Agent or Firm: Watson, Cole, Grindle &
Watson
Claims
What is claimed is:
1. A positioning joint for a folding ladder, comprising:
a first joint member having a first circular disc portion and a
tubular portion for the reception of a ladder frame, said disc
portion comprising a pair of spaced plates, and aligned slots
located in said first member;
a second joint member having a second circular disc portion with
first spaced open notches at the periphery thereof, and being
positioned between said plates and interconnected therewith for
relative pivotal movement about a common central axis between
unfolding and folding positions, said second member having a
tubular portion on said disc portion thereof for the reception of a
ladder frame;
a circular guide-disc plate positioned between said plates for
limited rotation about said common axis, said guide-disc plate
having second open notches at the periphery thereof at a spacing
and number corresponding to said first notches;
a locking device comprising a body portion extending through said
slots for sliding movement parallel to said common axis, said body
portion having a length greater than the spacing between said
plates of said first joint member, a stop plate on one end of said
body portion, a spring retainer on an opposite end of said body
portion, means between said spring retainer and one side of said
first joint member for resiliently urging said device into a locked
position in which said stop plate bears against an opposite side of
said first joint member, a short bar on said body portion extending
from said stop plate and having a length corresponding to the
spacing between said plates of said first joint member;
said guide-disc plate having an arcuate slot, and said second
circular disc having a projection pin engaging one end of said slot
in a relative position of said guide-disc plate in which said first
and second notches are misaligned in an unlocked position of said
members;
spring means acting between said guide-disc plate and said second
circular disc for urging said guide-disc plate into said unlocked
position;
a free end of said short bar bearing against a side of said
guide-disc plate in said unlocked position, and said spring means
effecting rotation of said guide-disc plate upon initial unfolding
of said members until one of said second notches aligns with said
short bar, continued unfolding effecting alignment of said one
second notch with one of said first notches such that said short
bar extends through said aligned notches in a locked position of
said numbers.
2. The joint according to claim 1, wherein said free end of said
short bar is wedge-shaped for avoiding engagement with said first
notches during a folding up said members together.
Description
BACKGROUND OF THE INVENTION
This invention relates to a positioning joint for a folding
ladder.
In a conventional positioning joint for a folding ladder, the
folding or unfolding of the ladder to a desired angular position is
performed by aligning holes in side discs and inserting a pin
through the aligned holes. A joint of this type has the
disadvantage that it is difficult to quickly align the holes
simultaneously.
Another prior art joint for a folding ladder utilizes a ratchet.
However, users must be concerned about the safety of such a joint
because of potential malfunctions of the ratchet.
A further positioning joint for a folding ladder utilizes a
U-shaped member as a control means, as set forth in U.S. patent
application Ser. No. 073,585. Two joint members are relatively
pivotable about a common axis, the joint members being lockable in
a series of predetermined angular positions by engaging a
spring-biased pawl, provided within one member, in notches formed
at the peripheral edge of the other member. A control means in
cooperation with a manually operated lever controls the locking and
unlocking of the joint.
Although this type positioning joint insures safety in use while
being easy to operate, it has a drawback in that its construction
is somewhat complex and costly to manufacture, and has a further
disadvantage in that it is cumbersome to operate the lever.
SUMMARY OF THE INVENTION
Accordingly, a principal object of the present invention is to
provide an improved positioning joint for a folding ladder, which
will reduce or eliminate the aforementioned defects, be able to
improve productivity with a simple structure, and insure safety in
use while at the same time be easy to operate.
According to the present invention, there is provided a positioning
joint for a folding ladder, in which two joint members are
relatively pivotable about a common axis, and are lockable in a
series of predetermined angular positions by engaging a locking
device provided within one member in notches formed at the
peripheral edge of the other member, under the control of a
guide-disc plate.
The invention includes a first joint member having a pair of spaced
slots for guiding a transversely slideable locking device, a
main-disc portion in the form of a pair of spaced-apart circular
plates, and a first tubular portion for fixing the ladder frame
therein. A sub-disc portion of a second joint member, and a
circular guide-disc plate are located between the spaced
plates.
The locking device has a body portion extending through the slots
and being longer than the spacing between the circular plates, a
stop plate on one end of the body portion, a spring retainer on the
opposite end of the body portion, and a spring located between the
spring retainer and one side of the first joint member for urging
the device into a locked position in which the stop plate bears
against an opposite side of the first joint member. A short bar
extends inwardly from the stop plate and has a length corresponding
to the spacing of the circular plates.
The second joint member has a second tubular portion for fixing the
ladder frame therein, and the sub-disc portion is connected to the
circular plates for relative pivotal movement about a common
central axis between unfolding and folding positions. The sub-disc
portion has a plurality of first spaced open notches at its
periphery.
The guide-disc plate is mounted for limited rotation about the
common axis, and has a plurality of second open notches at its
periphery at a spacing and number corresponding to the first
notches. The guide-disc plate has an arcuate slot, and the sub-disc
portion has a projection pin engaging one end of such slot in a
relative position of the guide disc plate in which the first and
second notches are misaligned in an unlocked position of the joint
members.
A spring interconnects the guide-disc plate and the sub-disc
portion for urging the guide-disc plate into the unlocked
position.
A free end of the short bar bears against a side of the guide-disc
portion in the unlocked position, and the spring effects rotation
of the guide-disc plate upon initial unfolding of the joint members
until one of the second notches aligns with the short bar.
Continued unfolding effects alignment of the one second notch with
one of the first notches such that the short bar extends through
the aligned notches in a locked position of the joint members.
The free end of the short bar may be wedge-shaped for avoiding
engagement with the first notches during a folding of the members
together.
Other features of the present invention will become apparent from
the following detailed description of the invention when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the positioning joint for a folding
ladder according to the invention;
FIG. 2 is a partially cutaway and exploded perspective view of the
FIG. 1 positioning joint;
FIG. 3A is a perspective view of the locking device according to
the invention;
FIG. 3B is an exploded perspective view of the locking device,
shown in FIG. 3A;
FIGS. 4A to 4E are sectional views of the FIG. 1 positioning joint
illustrating the increments by which the positioning joint is
operated; and
FIGS. 5A and 5B are transverse sectional views illustrating the
operation of the locking device in accordance with the
invention.
DETAILED DESCRIPTION OF THE INVENTION
The positioning joint for a folding ladder according to the
invention comprises, as shown in FIGS. 1 and 2, a first joint
member 1, a locking device 6, a second joint member 2 and a guide
disc plate 9.
The construction of the first joint member 1 is similar to a
conventional joint member, i.e., it may be formed, for example, of
sheet metal pressed into the shape of a main disc portion 1a having
two spaced-apart, parallel circular plates each with an axial
opening 3', and a first tubular portion 1b in which the upper end
of a ladder frame (not shown) is fixed. The first joint member 1 is
provided with two slots 5, 5' one in each side of the first tubular
portion 1b, so that a locking device 6 can be slideably mounted and
operated therein, as shown in FIG. 2.
The locking device 6 according to the invention comprises, as shown
in FIG. 3A and FIG. 3B, a body portion 6', a spring 7, a spring
retainer 6", and a screw 6"'. In the center of the spring retainer
6" is a central threaded hole through which screw 6"' extends for
attaching to the body portion 6'. Body portion 6' includes a bar 6b
of rectangular cross-section, a rectangular plate 6d fixed to one
end of bar 6b, an internally threaded tapped opening 6e at the
opposite end of bar 6b, and a short upper bar 6a of rectangular
cross-section fixed to the upper surface of bar 6b. The length of
bar 6a corresponds to the distance between the two spaced-apart
plates of the first joint member (FIG. 5B), and an end of bar 6a is
affixed to plate 6d. The other end of bar 6a being wedge-shaped as
at 6c so that when the positioning joint is unfolded it may firmly
engage the cut-out portions of a guide-disc plate 9, whereas when
the positioning joint is folded it may disengage the same.
The locking device 6 is mounted on first joint member 1 by
extending bars 6a, 6b through slots 5, 5' (FIG. 5A) so that the
plate 6d retains the locking device 6 against first tubular portion
1b. Spring 7 is then placed around bar 6b and screw 6"' with spring
retainer 6" in place is threaded into thread 6e.
The second joint member 2 comprises a sub-disc portion 2 a with a
central axial hole and a second tubular portion 2b in which the
upper end of another ladder frame (not shown) is fixed. The
sub-disc portion 2a has a circular stepped portion 8 with an axial
hole 3", a rectangular slot 13' having a first hook portion 15' for
hooking one end of a coil spring 14, a projection 12' formed at the
inner surface thereof for limiting the displacement of the guide
disc plate 9 by extending into an arcuate slot 12 of the guide-disc
plate, and a plurality of notches 10, 10' , 10" formed at the
peripheral edge.
The guide disc plate 9 has a central circular opening 8', so that
the plate can be rotatably fitted to the peripheral surface of the
circular stepped portion 8, a rectangular slot 13 having a second
hook portion 15 for hooking an opposite end of the coil spring 14,
and a plurality of cut-out portions 11, 11' , 11" at its peripheral
edge. The number and spacing of such cut-out portions corresponds
with the number and spacing of notches of the sub-disc portion
2a.
The guide disc plate 9 is coupled to the second joint member 2,
that is, the guide disc plate 9 is rotatably fitted by means of the
central circular opening 8' to the peripheral surface of the
circular stepped portion 8 of the second joint member, and opposite
ends of coil spring 14 are hooked onto hook portions 15, 15'
whereby the two rectangular slots 13, 13' are superimposed.
The joint members 1 and 2 are pivotably interconnected as a unit by
axial bolt 3, that is, the sub-disc portion 2a of the second joint
member 2, together with the guide disc plate 9, are located between
the spaced pair of circular plates of the first joint member 1, and
are pivoted on axial bolt 3 together with the first joint member
1.
The operation of the aforedescribed construction of the positioning
joint of the invention will be explained as follows with reference
to FIGS. 4A to 4E and 5A, 5B.
FIGS. 4A and 4B are sectional views of the positioning joint of the
present invention, FIG. 4A showing the joint in the unlocked fully
closed position, and FIG. 4B showing the joint in which bar 6a of
locking device 6 is locked into notch 11 and notch 10.
When unfolding the positioning joint from the fully closed position
of FIG. 4A in which end 6c of bar 6a bears against the confronting
side surface of plate 9, to the locked position in which bar 6a of
the locking device 6 is, as shown in FIG. 4B locked into the
cut-out portion 11 and the notch 10, bar 6a of the locking device 6
moves along the smooth side surface of the guide disc plate 9. When
the locking device 6 reaches the cut-out portion 11 of the guide
disc plate 9, the end 6c of the short bar 6a of the locking device
6 comes in contact with a surface of the sub-disc portion 2a and
passes through the cut-out portion 11 due to the resiliency of the
spring 7, thereby the guide disc plate 9 which was turning in a
counter-clockwise direction with the second joint member 2, turns
in a clockwise direction with the first joint member 1. If it is
unfolded further, the protrusion 12' of the sub-disc portion 2a
moves from the one end of arcuate slot 12 to the other end thereof,
and the coil spring 14 is continuously extended. Thereafter, it is
not until notch 10 of the sub-disc portion 2a is aligned with notch
11 that the locking device 6 is, as shown in FIGS. 4B and 5A,
locked as bar 6a passes through both notch 10 and notch 11 due to
the resiliency of spring 7.
To unfold the positioning joint further to a position in which
locking device 6 will be engaged in notch 10', reference is made to
FIGS. 4B to 4D and 5A to 5B. Upon manually pushing the spring
retainer 6" of the locking device 6 in the direction of the arrow
in FIG. 5B, the guide disc plate 9 is unlocked and turned in a
counter-clockwise direction by the contractile force of the coil
spring 14 until it is, as shown in FIG. 4C, stopped at the opposite
end of arcuate slot 12 from the position in FIG. 4B by means of the
protrusion 12' of the sub-disc portion 2a. Accordingly, when the
compressive force to the spring retainer 6" is released, since the
end of the short bar 6a of the locking device 6 is in contact with
a surface of the guide disc plate 9, it prevents the locking device
6 from falling back into the cut-out portion 11 and notch 10, and
joint members 1 and 2 are permitted to rotate without
interference.
Thereafter, the action is repeated but in a different position,
that is, when the locking device 6 reaches notch 11' of the guide
disc plate 9, the end of the short bar 6a of the locking device 6
comes in contact with a side surface of the sub-disc portion 2a and
thereafter passes through the notch 11' by the elastic force of
spring 7, such that the guide disc plate 9 which was turning in a
counter-clockwise direction relative to the second joint member 2,
turns in a clockwise direction relative to the first joint member
1. If it is unfolded further, the projection 12' of the sub-disc
portion 2a moves from one end of arcuate slot 12 to the other end
thereof, and the coil spring 14 is continuously extended.
Accordingly, it is not until notch 10' of the sub-disc portion 2a
is aligned with notch 11' of the guide disc plate 9 that the
locking device 6 is locked as bar 6a passes through both notch 10'
and notch 11' by the resiliency of the spring 7, as shown in FIG.
4D.
If it is intended to unfold the positioning joint further to engage
the locking device 6 in notch 10", as shown in FIG. 4E, the
positioning joint can be unfolded completely by the same operating
principle as aforedescribed.
The operation of folding the positioning joint is as follows. With
reference to FIG. 4E, upon pressing the spring retainer 6" of
locking device 6 in the direction of the arrow in FIG. 5B, the
guide disc plate 9 is unlocked and turned in a counter-clockwise
direction by the contractile force of coil spring 14 until it is
stopped at the opposite end of arcuate slot 12 from the position in
FIG. 4E by means of the projection 12' of the sub-disc portion 2a.
Accordingly, even if the compressive force on the spring retainer
6" is released, since the end 6c of the short bare 6a of the
locking device 6 is in contact with a side surface of the guide
disc plate 9, it prevents the locking device 6 from falling back
into notch 11" and notch 10", and joint members 1 and 2 are
permitted to rotate without interference. In this condition when
the positioning joint is folded, the end 6c of the short bar 6a of
locking device 6 is able to pass by notches 11, 11' and 11"
successively without being engaged by them, because its surface is
wedge shaped. Meanwhile, each of the notches 10, 10' and 10" are
never aligned with the corresponding notches 11, 11' and 11"
because projection 12' prevents the rotation of the guide disc
plate 9. As a result, the positioning joint according to the
present invention can be folded rapidly.
From the foregoing it can be seen that the present invention
provides an improved positioning joint for a folding ladder which
increases productivity due to simple, solid construction, and
insures safety in use while being easy and rapid to operate.
* * * * *